JP2633016B2 - Process cartridge and image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a laser beam printer, and more specifically, a means for charging a movable image carrier surface to the image carrier surface. The present invention relates to an image forming apparatus of a type in which image formation is performed by an image forming unit including the image forming apparatus, and an image bearing member surface used for image formation is cleaned by a cleaning unit and repeatedly used for image formation, and a process cartridge detachable from the apparatus.

[Conventional technology]

As a specific example of the image forming apparatus of the type described above,
A transfer type electrophotographic copying device, a transfer type electrostatic recording device, and the like can be given.

The transfer type electrophotographic copying apparatus uses a drum type or endless belt type electrophotographic photosensitive member which is rotated or driven to rotate as an image carrier, and the photosensitive member surface is uniformly charged and charged.
A developed image is formed by applying an image forming process based on image exposure and development, and the developed image is transferred to a transfer material surface by a transfer device, and the transferred developed image is fixed to the transfer material surface by a fixing device. Then, the transfer material is output as an image-formed product. The surface of the photoreceptor after the image transfer is cleaned by a cleaning unit and repeatedly provided for image formation.

The transfer type electrostatic recording apparatus uses a drum-type or endless-type dielectric which is rotated or rotated as an image carrier, and uniformly charges and selectively removes electric charge on the dielectric surface.
A developed image is formed by applying an image forming process means based on development, and thereafter, the transferred image is formed on the transfer material surface by transferring and fixing the developed image to the transfer material surface in the same manner as in the electrophotographic copying apparatus described above. The dielectric surface after image transfer is cleaned by a cleaning means and repeatedly provided for image formation.

The cleaning unit removes untransferred developer (toner), transfer material paper dust, and other contaminants remaining on the surface of the photosensitive member or the dielectric as an image carrier after image transfer to the transfer material surface. Generally, a configuration is used in which a rubber elastic member such as urethane rubber is used, and this member is brought into contact with the surface of the image carrier to wipe off and remove adhered contaminants on the surface of the image carrier.

A corona discharger such as a corotron or a scorotron, which has good uniform charging properties, is widely used as a means for uniformly charging a surface of a photoreceptor or a dielectric as an image carrier. However, the corona discharger requires an expensive high-voltage power supply, and requires space such as itself and a shield space for the high-voltage power supply.
Also, many corona products such as ozone are generated, and additional means and mechanisms are needed to deal with them.
There is a problem that it is a factor that increases the cost.

Therefore, recently, the use of a contact charging system instead of the corona discharger, which has many problems, has been studied. In contact charging, a voltage (for example, 1 to 2 KV)
About a direct current voltage, or a superimposed voltage of a direct current voltage and an alternating current voltage) is brought into contact with a conductive member (contact charging member) to directly inject electric charge into the image carrier surface to thereby fix the image carrier surface to a predetermined position. Roller charging type (JP-A-56-91253) and blade charging type (JP-A-56-1925).
Nos. 04349 and 60-1477756) and a charging / cleaning combined use type (JP-A-56-165166) have been devised.

[Problems to be solved by the invention]

In the contact charging method, it is important to apply the charging member to the surface of the image carrier, which is the member to be charged, in a state where the charging member is uniformly contacted at each portion along the length thereof, and a uniform contact state cannot be obtained. In this case, charging unevenness occurs on the surface of the image carrier.

On the other hand, in consideration of simplification of the apparatus and cost reduction, a blade charging type is most preferable as shown in, for example, JP-A-56-104349.

However, uniform charging may not be obtained due to wear and damage of the image carrier surface caused by the blade-shaped contact charging member or the blade-shaped cleaning member being pressed against the image carrier.

[Object of the invention]

The present invention has been made in view of the above points, and makes the contact setting of the contact charging member to the image carrier highly accurate, that is, the contact charging member is uniformly applied to the image carrier surface at each portion along the length thereof. It is an object of the present invention to ensure that a stable contact state is maintained at all times to uniformly charge the surface of an image bearing member.

Another object of the present invention is to provide an image forming apparatus and a process cartridge capable of obtaining a good image by uniformly charging the surface of an image carrier.

[Configuration of the invention]

In order to achieve the above object, the present invention provides a movable image carrier, a cleaning blade that contacts the surface of the image carrier and cleans the image carrier, and the image cleaned by the cleaning blade. A charging blade that contacts the surface of the carrier to charge the image carrier, wherein the cleaning blade and the charging blade have their edges in contact with the image carrier, and the charging blade The contact pressure (g / cm) of the cleaning blade against the image carrier is smaller than the contact pressure (g / cm) of the cleaning blade against the image carrier. Alternatively, the present invention is a process cartridge detachable from the image forming apparatus, wherein the movable image carrier, a cleaning blade that contacts the surface of the image carrier to clean the image carrier,
A charging blade that contacts the surface of the image carrier that has been cleaned by the cleaning blade and charges the image carrier.In a process cartridge, the cleaning blade and the charging blade have their edges attached to the image carrier. And a contact pressure (g / cm) of the charging blade against the image carrier is smaller than a contact pressure (g / cm) of the cleaning blade against the image carrier. .

〔Example〕

FIG. 1 is a schematic view of the configuration of an embodiment of the apparatus. This example is a transfer type electrophotographic copying machine of a process cartridge detachable type.

In FIG. 1, reference numeral 1 denotes a drum-type electrophotographic photosensitive member (hereinafter abbreviated as a photosensitive member) as an image carrier that is driven to rotate at a predetermined peripheral speed in a direction indicated by an arrow around a spindle 1a. Reference numeral 2 denotes a contact charging member as a means for uniformly charging the peripheral surface of the photoreceptor. In this embodiment, a conductive elastic blade made of conductive rubber or the like or an outer surface thereof has an appropriate resistance value (for example, a volume resistivity of 10 ⁸ to 10 ⁸ ). Ten
¹² Ω · cm). Reference numeral 3 denotes a short focal length lens array as an optical image exposure means, 4 denotes a developing device, 5 denotes a transfer device, and 51 synchronizes the transfer material P conveyed one by one from a paper feeding unit (not shown) with the rotation of the photosensitive member 1. A timing roller 52 for feeding between the photosensitive member 1 and the transfer device 5
Is a transfer material guide member disposed between the timing roller 51 and the transfer device 5, and 52 is a fixing device (not shown) for transferring the transfer material P, which has passed through the space between the photoreceptor 1 and the transfer device 5 and has undergone image transfer. And a cleaning device 6 for cleaning the surface of the photoconductor 1 after image transfer.

The apparatus of the present embodiment includes a photosensitive member 1, a contact charging member 2, and a developing device 4.
The four process devices of the cleaning device 6 are configured as a process cartridge 7 in which they are collectively incorporated in a predetermined arrangement relationship with each other, and the process cartridge 7 is supported in the copier body by support rails 8.8.
, And can be freely pulled out of the copier body. The process cartridge 7 is not limited to the above example, and includes the photosensitive member 1 serving as an image carrier and at least one of the contact charging member 2, the developing device 4, and the cleaning device 6, which are process devices contributing to image formation. What is necessary is just to be comprised.

By fully inserting and mounting the process cartridge 7 into the main body of the copying machine, the main body of the copying machine and the side of the process cartridge 7 are mechanically and electrically coupled to each other, and the copying machine can be operated.

In the course of rotation, the peripheral surface of the photosensitive member 1
Is charged uniformly by the blade 2 which is a contact charging member to which a voltage (for example, a superimposed voltage of an alternating voltage with a DC voltage) is applied, and then passes through the position of the light image exposure means 3 to expose the light image exposure L (original). (Slit exposure of the image), an electrostatic latent image corresponding to the exposure light image pattern is sequentially formed. Reference numeral 7a denotes a light transmitting window hole opened in the cartridge housing wall corresponding to the light image exposure means 3. The hole image exposure L can be performed by laser beam scanning. In the case of an electrostatic recording apparatus, latent images are sequentially formed on the photoconductor surface by means such as an electrode array that selectively removes electricity from the photoconductor surface.

The latent image formed on the surface of the photoreceptor 1 is subsequently developed (developed) as a toner image by a developing device 4, and the toner image on the surface of the photoreceptor is transferred between the transfer device 5 and the photoreceptor 1 by a transfer device 5. One sheet is conveyed from a sheet feeding unit (not shown), and is transferred to the surface of the transfer material P fed in synchronization with the rotation of the photoconductor 1 by the timing roller 51.

The transfer material P having received the image transfer through the transfer device 5 is sequentially separated from the surface of the photoreceptor 1, is introduced into a fixing device (not shown) by a feeding device 53, undergoes image fixing, and is output as an image formed material. Is done.

On the other hand, the surface of the photoreceptor 1 after the image transfer is cleaned and cleaned by the cleaning member 6A of the cleaning device 6 to remove transfer residual toner, transfer material paper dust, and other residual deposits, and is repeatedly subjected to image formation. You.

The cleaning member 6A is a blade-shaped wiping member (hereinafter, referred to as a cleaning blade) made of urethane rubber or the like abutted on the surface of the photosensitive member 1 at the leading edge portion. It is scraped off and removed.

The cleaning blade 6A contacting the photoconductor 1 surface is
In particular, when the photoreceptor 1 has a surface containing a resin such as OPC as a component, the contact frictional force with the photoreceptor increases, and scratches due to rubbing of the photoreceptor as the image carrier are likely to occur. Such flaws naturally lead to image defects during image formation, particularly image defects due to poor charging.

On the other hand, transfer material paper dust and other residues other than the toner on the photoreceptor strongly adhere to the photoreceptor, so that the photoreceptor needs to be shaved to some extent with a cleaning blade.

Actually, the toner wiped from the surface of the photoreceptor 1 is present at the contact portion between the cleaning blade 6A and the photoreceptor 1, and this acts as an appropriate lubricant to reduce the dynamic friction coefficient. Scratches on the photoreceptor are less likely to occur, and it is possible to appropriately remove adhering substances other than toner on the photoreceptor.

On the other hand, the contact charging blade 2 has a cleaning blade 6A.
As shown in FIG. 1, the leading edge of the blade comes into contact with the surface of the photoreceptor 1 which has been cleaned as described above. Therefore, the effect of reducing the dynamic friction coefficient by using the toner as a lubricant as in the case of the cleaning blade 6A is used. However, the photosensitive member is easily damaged.

Here, the pressing force of the blade against the photoconductor due to the generation of the scratch on the photoconductor will be examined.

The contact force per unit contact length of the cleaning blade 6A (the length where the image carrier and the blade are in contact) is P ₁
(G / cm) The contact force per unit contact length of the charging blade 2
P ₂ (g / cm).

Here, the surface layer (CTL layer) of the organic (OPC) photoreceptor uses a binder mainly composed of a styrene-based or polycarbonate-based resin, and a contact pressure of a charging blade and an OPC photoreceptor mainly composed of a polycarbonate-based resin. 2 is indicated by the solid line in FIG. This is the maximum flaw depth when the photosensitive member travels 180 m with only the charging blade in contact with the photosensitive member.

Thus, the maximum scratch depth of the photoreceptor exists in the pressing force of the blade against the photoreceptor, Is established. Here, V represents the maximum scratch depth of the photoconductor, κ is a coefficient relating to friction between the photoconductor and the blade, L is the traveling distance of the photoconductor, P is the blade pressure on the photoconductor, and _Pm is the photoconductor. Is a coefficient representing the hardness and fragility of the sample.

When the cleaning blade 6A and the charging blade 2 are compared, P _m and the running distance L are constant because both are a single photosensitive drum, and the difference between them is determined by κ and P. Here, although the output of the image differs depending on the developing method and the latent image condition, in this experiment, a fine halftone image with a maximum flaw depth of about 1.0μ, but a streak-like flaw image was confirmed on the transfer material. .

Here, unlike the charging blade, the residual toner is present on the photoreceptor in the kneeling blade 6A as described above, and acts as rolling particles to reduce the frictional property κ attributed to substantial scratches. Therefore, cleaning blade 6A
The maximum damage depth on the photoconductor where residual toner is present by contacting only the photoconductor with the photoconductor is reduced as compared with the case where the photoconductor is not provided with only the charging blade. Here, the dotted line in FIG. 2 shows the relationship between the contact pressure of the cleaning blade 6A and the maximum scratch depth of the OPC photoconductor mainly composed of the polycarbonate resin. In this experiment, a one-component magnetic toner having an average particle diameter of 11 μm and silica externally added was used as the toner, and the blade pressing force and the maximum damage depth of the photoconductor were slightly different depending on the material and shape of the toner. Are almost the same. As described above, one of the factors of the life of the photoconductor is the pressing force between the charging blade 2 and the cleaning blade 6A, particularly the pressing force of the charging blade 2 against the photoconductor. However, if the contact pressure of the cleaning blade 6A with respect to the photoreceptor is too small, a cleaning failure occurs.
Residual deposits on the photoreceptor are moved to the charging surface of the charging blade, so that the residues accumulate on the charging blade surface to cause poor charging. Here, in the above experiment, a cleaning blade 6A having good cleaning properties when using an OPC photoreceptor having a polycarbonate resin as a main component and a one-component magnetic toner having an average particle diameter of 11 μm externally added with silica was used.
The minimum pressing force against the photoreceptor was 15 g / cm. However, as shown by the solid line in FIG. 2, when the charging blade pressing force against the photoconductor is 15 g / cm or more, the maximum scratch depth of the photoconductor becomes 1.0 μ or more, and the image on the transfer material has defects as described above. I do. Therefore, it is necessary to make the pressure contact force of the charging blade against the photoconductor smaller than 15 g / cm. That is, the charging blade 2 for the photoreceptor having no toner
Must be smaller than the pressure of the cleaning blade 6A.

On the other hand, as a photoconductor, an OP containing a styrene-based resin as a main component is used.
FIG. 2 shows the relationship between the pressing force of the blade against the photoconductor and the maximum damage depth of the photoconductor when the C photoconductor is used.
Here, the solid line indicates the case where only the charging blade 2 is in contact with the photoconductor, the dotted line indicates the case where only the charging blade 2 is in contact with the photoconductor, and the other conditions are the same as those described above. . At this time, the minimum pressing force of the cleaning blade 6A with respect to the photoreceptor at which the cleaning property is good is 14 g / cm.
Met. Here, when the pressing force of the charging blade 2 is set to 13 g / cm or more as shown in the solid line in FIG.
1.0 μm or more, and image defects occur. Therefore, the pressing force of the charging blade must be smaller than 13 g / cm, and also in this case, the pressing force of the charging blade 2 needs to be smaller than the pressing force of the cleaning blade 6A.

Note that the minimum pressing force of the cleaning blade 6A against the photoreceptor at which the cleaning property is good depends on the photoreceptor and the toner. For example, the smaller the average particle size of the toner and the larger the external addition amount of silica, the larger the contact pressure of the cleaning blade 6A with the photoconductor must be.

Further, the maximum scratch depth of the photoconductor changes depending on the traveling distance of the photoconductor, that is, the number of durable sheets of the image forming apparatus, and the maximum scratch depth of the photoconductor reaches a depth at which image defects occur. The time may be set to the life of the process cartridge.

Further, the charging blade 2 is liable to be turned up with respect to the cleaning blade 6A in which the dynamic friction coefficient is reduced due to the interposition of a residual deposit between the photosensitive member and the photosensitive member. When the charging blade 2 is turned up in this way, charging failure of the photoconductor is caused, or the blade is deteriorated. Therefore, if the pressing force of the charging blade 2 against the photosensitive member is made smaller than the pressing force of the cleaning blade and the life of both blades is matched, it is effective for a process cartridge composed of both blades and an image carrier.

The following method is used to provide a pressure difference between the cleaning blade 6A and the charging blade 2 with respect to the photosensitive member. Assuming that the suffix is 1 for the cleaning blade and 2 for the charging blade, the thickness t ₁ > for forming the pressure contact force P ₁ > P ₂ >
It is determined by t ₂ , free length l ₁ <l ₂ , elastic modulus E ₁ > E ₂ , displacement δ ₁ > δ _{2, and the} like, and combinations thereof.

In addition, by setting the same settings for the free length of both blades, the elastic modulus of the material, and the amount of displacement, the accuracy, manufacturing assembly, and simplification of inspection are measured, and the pressure difference is reduced in cross-sectional shape as shown in FIG. Can be set by changing. In FIG. 3, (c), (a) and (b) are arranged in descending order of pressure.

As shown in FIG. 4, the cleaning blade 6A forms an acute angle between the blade and the tangent of the photoreceptor 1 at the contact position on the photoreceptor 1 at the contact position with the photoreceptor 1 (FIG. 4 (a)). )) It may be in contact with the so-called forward direction, or may be in contact with the so-called counter direction with the angle being an acute angle. Further, the charging blade 2
Also, the photoconductor 1 is not limited to the one in which the photoconductor 1 is brought into contact in the counter direction as shown in FIG.

Usage example OP with polycarbonate resin as the main component for photoreceptor 1
Using C photoreceptor, cleaning blade 6A with JISA hardness 65
° using a urethane rubber blade, it abuts on the photosensitive member 1 at a contact pressure 15 gr / cm, contact charging blade 2 as 10 ⁶ to 10
^{Using a 9} Ω · cm conductive EPDM rubber blade, it was brought into contact with the photoreceptor at a contact pressure of 10 g / cm, which was lower than the contact pressure of the knealing blade 6A.
_An endurance test was performed by applying a bias voltage of 1500 V and a frequency of 800 Hz to obtain a charging potential of about 700 V on the photoreceptor surface.

In addition, the charging blade has an insulating layer (100 ⁸
~ 10 ¹² Ω · cm).

As described above, since the contact pressure of the contact charging blade with respect to the photoreceptor was made smaller than the contact pressure of the cleaning blade, no image defects occurred due to the damage of the photoreceptor due to the charging blade even during 3,000 sheets.

〔The invention's effect〕

As described above, according to the present invention, the contact state of the charging blade with respect to the image carrier is stabilized, stability of contact charging is obtained, and damage to the image carrier can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the image forming apparatus of the present invention, FIG. 2 is a graph showing the relationship between the contact pressure of the blade on the image carrier and the depth of the image carrier flaw, and FIG. FIG. 4 is a cross-sectional view showing the shape of the blade applicable to the present invention, and FIG. 4 is a cross-sectional view showing the contact direction of the charging blade and the cleaning blade with respect to the image carrier. 1 is a photoconductor, 2 is a charging blade, 6A is a cleaning blade, and E is a power supply.

Claims (4)

(57) [Claims] An image carrier that is movable, a cleaning blade that contacts the surface of the image carrier to clean the image carrier, and a cleaning blade that contacts the surface of the image carrier that is cleaned by the cleaning blade. A charging blade that charges the image carrier with the cleaning blade and the charging blade. The edges of the cleaning blade and the charging blade are in contact with the image carrier, and the contact pressure of the charging blade against the carrier ( g / cm) is smaller than a contact pressure (g / c /) of the cleaning blade against the image carrier. 2. The image forming apparatus according to claim 1, wherein each of the cleaning blade and the charging blade forms a line between a tangential line at a contact point between the blade and the image carrier, the line being located downstream of the contact point in the moving direction of the image carrier. 2. The image forming apparatus according to claim 1, wherein the corner is an acute angle. 3. A process cartridge detachable from an image forming apparatus, comprising: a movable image carrier; a cleaning blade for contacting a surface of the image carrier to clean the image carrier; A charging blade that contacts the surface of the image carrier that has been cleaned by the charging blade to charge the image carrier, and wherein the cleaning blade and the charging blade have their edges in contact with the image carrier, A process cartridge wherein a contact pressure (g / cm) of the charging blade against the image carrier is smaller than a contact pressure (g / cm) of the cleaning blade against the image carrier. 4. The image forming apparatus according to claim 1, wherein each of the cleaning blade and the charging blade forms a tangential line at a contact point between the blade and the image carrier, the line being downstream of the contact point in the moving direction of the image carrier. 4. The process carnage of claim 3, wherein the corners are acute.